The renewed relations with the U.S. may have been prompted by the Cuban revolutionaries' connection with Pope Francis.

HAVANA — Rumors that Fidel and Raul Castro are returning to the Catholic faith are growing in substance. As current President Raul Castro charts a new course for the Communist country, the brothers are reportedly rediscovering the faith they grew up in.

In their youth, the Castro boys attended the Colegio de Dolores, a prestigious Jesuit school in the city of Santiago de Cuba. The Castros later strayed from their upbringing, and after the 1959 revolution, Fidel closed the country's Catholic schools and expelled all Jesuits.

The Marxist government even prohibited celebrating Christmas because it interfered with the sugarcane harvest. Little changed in Havana's attitude towards organized religion until Pope John Paul II's 1998 visit, which began to improve Church-state relations.

When Benedict XVI assumed the papacy, Fidel told him that "spiritual reflections" had become a significant part of his life. But it was the election of the first Latin American pope, Francis, who also happens to be a Jesuit, that truly reconciled the erstwhile revolutionary with the Catholic Church.

When Francis visited the island last September, Fidel showed him underlined sentences from John Paul II's 1998 speech in Cuba: "Cuba must open itself to the world, and the world must open itself to Cuba." (There have long been reports that say it was Francis himself — then archbishop of Buenos Aires — who wrote those words, a story he has never denied.)

Francis responded to Fidel Castro's gesture by giving him a collection of writings by his favorite teacher at the Colegio de Dolores, who died in exile. Castro told the pope that he "became a revolutionary thanks to the Jesuits," noting it was them "who taught [him] to reason and always challenge authority."

People close to Fidel, 89, think his return to the faith could still be a slower process, but that Raul's may happen more quickly. The 84-year-old current president told Pope Francis during his visit to Rome that his return to the Church's pastoral mission was the reason for his own reconciliation with Catholicism. While he may have said it for the cameras, declarations he has made since — he told French President Francois Hollande that "if the pope continues like this, [he] will return to the Church" — prove there is substance behind the words.

It remains to be seen whether Raul's reconciliation will lead to a public announcement of his rediscovered faith — and whether it will come before his expected retirement in 2018. Fidel's gestures, meanwhile, are even harder to predict.